<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
</head>
<body>
<script type="text/javascript">
	var arr = ['aa','bb','cc'];
	var a = '12345678';
	alert(a.length)

	//alert(arr.join());			//弹出字符串'aa,bb,cc'	长度为8不为6
	alert(arr.join(''));		//弹出字符串 'aabbcc'	长度为6
	//alert(arr.join('-'));			//弹出'aa-bb-cc'		长度为8
</script>
</body>
</html>